1. Field of the Invention
The present invention concerns a method of initializing a link between a mobile terminal of a public mobile network and a domestic base station, for example a base station of a public switched network.
The invention also concerns an initialization service for a link of the above kind.
2. Description of the Prior Art
The invention concerns cordless telephones. Cordless telephony systems (CTS) are currently available in the form of handsets or terminals and base stations having a radio link of limited range, for example limited to domestic use within an apartment or a house. In the future such telephone systems may operate in frequency bands already covered and used by public mobile network operators. This gives rise to a problem of frequency management.
Another problem is the management of security parameters of the links between the handsets and the base stations.
Yet another problem is that of the multiplicity of portable handsets; a user can have one portable handset for a public mobile network and another handset for a cordless telephone. GB-A-2 282 735 mentions that it has been suggested that the same portable handset could be used for the public mobile network and for the public switched network. The above document explains that this solution is not advantageous because of the resulting complications in frequency management needed to prevent interference between separate domestic base stations or devices need to prevent such interference, for example by dynamic allocation of channels.
The use of a single portable handset for the public mobile network and for a domestic base station is envisaged in the GSM CTS system currently undergoing standardization, for example. One feature of this system is the subset or subsets of frequencies used for communication between a domestic base station and the single mobile terminal for the public mobile network used to communicate with a domestic base station.
The use of a dynamic scheme of channel allocation, as suggested in GB-A-2 282 735, requires the domestic base station and the mobile terminal to be initialized with the same parameters, for example to have the same starting frequency and to use the same frequency changing algorithm. A first solution to this problem is to initialize the portable handsets and the domestic base stations with the same parameters; this rules out individual allocation of channels and dynamic allocation of channels; this further rules out selling the domestic base stations and the handsets separately.
GB-A-2 282 735 proposes a device for automatically routing calls to a portable handset of a public mobile network or to the conventional switched telephone network according to the distance between the portable handset and a domestic base station; the above document proposes automatic routing of calls to the switched telephone network when the handset is near the base station; the proximity of the handset is detected by low-power narrow-band telemetry signals transmitted by the handset. This solution does not solve the problem of the multiplicity of handsets or the problem of frequency management raised by the extension of public mobile network frequencies.
The invention therefore proposes a solution to the problem of managing parameters of cordless telephone systems enabling the use of the same portable handset for a link to a public mobile network and for a link to a domestic base station. It also enables a network operator to control the parameters of the links with the domestic base stations.
It also solves the new problem of initializing domestic base stations in mobile telephone systems using a single portable handset.
It further solves the new problem of variation in time of the position of the domestic base station and enables tracking of link parameters allocated to domestic base stations.
The invention has the advantage of enabling management of the parameters of links with domestic base stations by the administrator of a public mobile network. It enables the mobile terminals and the base stations to be sold separately. It assures authentication of the mobile terminal and the base station with a high level of security.
To be more precise, the invention proposes a method of initializing a link between a mobile terminal of a public mobile network and a domestic base station, comprising:
authentication of the mobile terminal by the public mobile network,
transmission of data for initializing the link with the domestic base station to the terminal from the public mobile network, and
transmission of said data from the mobile terminal to the domestic base station.
In one embodiment the method further comprises a step of the mobile terminal calling a special service number before the authentication step.
The link initialization data advantageously depends on the location of the mobile terminal during the authentication step.
In another embodiment, the initialization data includes time information.
The authentication step can include the normal authentication of the mobile terminal by the public mobile network. It can also include transmission by the mobile terminal of information required for initializing the link, such as the type of domestic base station.
In one embodiment, the step of transmitting data from the mobile terminal includes the storage of the initialization data in a smart card of the mobile terminal and insertion of said smart card into a card reader of the domestic base station.
In another embodiment, the step of transmitting data from the mobile terminal includes the transmission of data from the mobile terminal to the base station over a link separate from the link to be set up. The separate link can be a contactless link such as an infrared link or a microwave link for contactless cards.
The method can include a step of authorizing data transfer before the step of transmitting data from the mobile terminal.
The domestic base station is a public switched network terminal, for example, or a private automatic branch exchange terminal.
The invention also proposes a service for management of links between mobile terminals of a public mobile network and domestic base stations, comprising:
authentication of a mobile terminal by the public mobile network, and
transmission of data for initializing the link with a domestic base station to the terminal from the public mobile network.
In one embodiment, the service further includes a step of receiving a call from a mobile terminal before the authentication step.
The link initialization data advantageously depends on the location of the mobile terminal during the authentication step.
The initialization data preferably includes time information.
In one embodiment, the authentication step includes the normal authentication of the mobile terminal by the public mobile network. It can also include transmission by the mobile terminal of information required for initialization of the link, such as the type of domestic base station.
The invention further proposes a domestic base station comprising a smart card reader.
Finally, it concerns a cordless telephone system comprising a domestic base station, a mobile terminal and a link between the base station and the terminal separate from the telephone link.
The separate link is preferably a contactless link such as an infrared link or a microwave link for contactless cards.
Other features and advantages of the invention will become apparent from a reading of the following description of embodiments of the invention given by way of example only and with reference to the GSM CTS.